Inkjet printing device

ABSTRACT

The invention relates to an inkjet printing apparatus ( 1 ) with at least one printing head ( 2 ). Several tanks ( 3, 4 ) for inks and/or a cleaning medium are arranged in front of a connection opening ( 7 ) for the printing head ( 2 ), and the tanks ( 3, 4 ) are connected by feed lines ( 5 ) with the connection opening ( 7 ) for the printing head ( 2 ), whereby a stop element ( 6 ) is arranged between each tank ( 3, 4 ) and the connection opening ( 7 ).

The invention relates to an inkjet printing apparatus and a printinghead for inkjet printing apparatus, as described in the preamble ofclaims 1 and 31.

Inkjet printing apparatus or inkjet printers are already known, in whichan ink tank or ink reservoir is placed in front of a nozzle or a groupof nozzles of a printing head for applying or discharging inks. The inkreservoir is connected via channels to the nozzle or group of nozzles onthe one hand and via a feed line to the ink tank on the other hand. Thedisadvantage of this was that due to this method of supplying inkprinting devices could only be produced that could handle one type ofink. In order to work with different types of ink the machine needed tobe completely reset.

The demand for inkjet printers that use various different ink systems,i.e. inks of different kinds, is particularly high in large scaleproduction, where the same printing apparatus needs to be used forprinting different materials, such as paper, cardboard, plastic film oreven textiles. Solutions to this problem have already been proposedwhich enable an inkjet printer to be reset to use different ink systems.

In U.S. Pat. No. 6,024,441 A an inkjet printing apparatus is described,comprising ink storing tanks, flexible feed lines and connecting unitsfor the printing heads. For different colours from different ink systemsfeed lines run from the ink tanks to a connecting unit belonging to anink system The printing heads of the inkjet printing apparatus are inturn connected to printing head connecting portions on the printing headconnecting units, whereby the supply of ink to the printing heads isensured. In order to reset the inkjet printing apparatus to a new inksystem it is necessary to remove the printing heads from the inkjetprinting apparatus by releasing the printing head connecting portionsfrom the printing head connecting units. The printing heads are thenexchanged and the new set of printing heads are connected to theprinting head connecting units of the new ink system. The exchange ofthe ink system in inkjet printing apparatus as described in U.S. Pat.No. 6,024,441 A thus requires a considerable amount of manipulation toremove or install the printing heads.

The objective of the present invention is to create an inkjet printingapparatus which can be used universally without the need for longresetting times at the inkjet printer.

The objective of the invention is achieved by claim 1. It isadvantageous in this embodiment that with one set of printing headsdifferent ink systems or inks with different properties, viscosity,colour, colour concentration etc. can be used. In order to reset theprinter the different tanks only need to be connected with the printingheads by adjusting the stop elements appropriately, it is not necessaryto changed the printing heads or completely convert the inkjet printingapparatus or inkjet printer, and the advantages of each type of ink canstill be utilised with one single inkjet printing apparatus.

The development of the inkjet printing apparatus according to claim 2has the advantage that an intermediate or buffer store for storing inkis provided by the reservoirs, and this provides a safeguard against aninterruption of operation due to empty tanks.

The development of the inkjet printing apparatus according to claim 3has the advantage that the required amount of ink can flow into theprinting head and thus any reduction in print quality can be avoided.

By means of the development of the inkjet printing apparatus accordingto claim 4, in which a reservoir is arranged in the printing head,inkjet printing apparatus can be produced in an advantageous manner witha much more compact structure.

A development of the inkjet printing apparatus according to claim 5 isalso advantageous, as thereby fewer components need to be used. By usinga common multiway valve as a stop element the risk of malfunction isalso reduced, as it is not possible for ink or cleaning medium to flowinto the printing head simultaneously from several tanks.

The development of the inkjet printing apparatus according to claim 6has the advantage that the feeding of ink or cleaning medium into theprinting head is independent of the effect of gravity and thus the tankscan be arranged in any area of the inkjet printer. The conveyance of theink or cleaning medium is ensured in each case by the pumps.

By means of the design of the inkjet printing apparatus according toclaim 7 in an advantageous manner impurities are prevented from enteringinto the printing head and the nozzles cannot become blocked.

The development according to claims 8 and 9 is also advantageous asthereby the pressure balancing of ink in the printing head or in thecorresponding reservoir can be achieved by the pressure in thecorresponding tank.

By means of the developments of the inkjet printing apparatus accordingto claims 10 to 14, the inks can always be kept within an optimumoperating temperature range for processing, and the supply of theprinting head with ink can be automated and in particular controlled byprogram.

The design of the inkjet printing apparatus according to claim 15 hasthe advantage that thereby inkjet printing apparatus can be manufacturedto have a very broad range of applications. Inkjet printers with inkjetprinting apparatus of this kind can be used in inkjet printers ofvarying designs and in very different areas of application.

The development according to claim 16 is also advantageous as thecleaning of the printing heads made possible thereby shortens the timeneeded for resetting inkjet printing apparatus to a new ink systemconsiderably, and misprints caused by the temporary and undesired mixingof inks of different types can be avoided.

The development of the inkjet printing apparatus with a filling heightsensor according to claims 17 and 18 has the advantage that the fillingheight of inks in the reservoirs can always be determined. It can alsobe ensured that there is always a sufficient amount of ink in thereservoirs and the supply of ink in the reservoirs can be prevented fromrunning out, thus preventing the interruption of printing and as aresult the production of misprints.

By means of the design of the inkjet printing apparatus according toclaims 19 to 22, in which the reservoirs or the distribution chamber areprovided with ventilation openings or a pressure control valve, inparticular a servo valve, it is ensured in an advantageous manner thatthe ink can flow unimpeded from the reservoirs into the area of thespray devices. In this way pressure variations in the distributionchamber of the printing head are avoided and ink drops of varying sizescannot be expelled from the printing head, which influences the qualityof the print.

The development of the inkjet printing apparatus according to claim 23has the advantage that dust particles from the environment cannot enterthe printing head and cause the nozzles of the printing head to becomeblocked as a result.

The development of the inkjet printing apparatus according to claims 24and 25 is also advantageous, as thereby pressure fluctuations disruptingthe flow of ink in the feed lines or the reservoirs can be reduced.Variations in pressure are caused mainly by the acceleration forcesacting on the ink which occur during the movement of the printing headin transverse direction over the printing medium.

The design of the inkjet printing apparatus according to claim 26 isadvantageous in that if an ink is not actually in use the latter isconveyed in a circuit and thus the components or ingredients of the inkcannot be deposited in the lines.

The design of the inkjet printing apparatus according to claim 27 isadvantageous in that the arrangement of the ink tanks can be made morecompact, in particular a smaller number of tanks for the various coloursof inks of the different ink systems can be found to be sufficient.

A development of the inkjet printing apparatus according to claims 28and 29 is also advantageous as thereby the control of the variousoperating states of the inkjet printing apparatus can be automated orprogram controlled.

The development of the inkjet printing apparatus according to claim 30has the advantage that the supply of the inkjet printing apparatus withink or the required cleaning medium can be ensured over longer periodsand thus the operation of the inkjet printing apparatus can be ensuredwithout interruption.

The objective of the invention is achieved independently by means of aprinting head according to the features in the characterising part ofclaim 31. It is an advantage here that one set of printing heads can beused for the required number of colours and inks of different inksystems. In order to adjust between the various ink systems it is merelynecessary to close or open the stop elements of the printing headaccordingly. A further advantage is that when adjusting to a new inksystem the ink residue remaining in the reservoirs does not have to beremoved and thus material losses can be reduced.

By means of the printing head according to claims 32 to 34 in which thereservoirs are designed to have ventilation openings it is ensured in anadvantageous manner that the ink can flow from the reservoirs in thecorrect amount for uninterrupted operation in the region of the spraydevices.

It is ensured by the development of the printing head according to claim35 that no dust particles or impurities from the air enter the nozzlesof the printing head and cause a blockage of the latter.

The development of the printing head according to claim 36 is alsoadvantageous as it is possible thereby to keep the inks within theoptimum range of temperatures for processing.

The development of the printing head according to claim 37 makes itpossible in an advantageous manner to use such printing heads forworking various ink systems and to use them in inkjet printers of verydifferent kinds.

By means of the printing head according to claim 38 it is possible toreduce the time required to reset for processing ink from a new inksystem and thus avoid the losses of inks through undesired mixing of theinks from different ink systems.

For a better understanding of the invention the latter is explained inmore detail with reference to the following drawings.

In a schematically simplified view:

FIG. 1 shows an inkjet printing apparatus with a printing head;

FIG. 2 shows a printing head with several reservoirs for inks or acleaning medium;

FIG. 3 shows a detail of an inkjet printer with three inkjet printingapparatus according to FIG. 2 in perspective and in simplified view.

First of all, it should be noted that in the variously describedembodiments the same parts are allocated the same reference numbers andthe same component names, whereby the disclosures contained throughoutthe description can be applied accordingly to the same parts with thesame reference numbers or same component names. The details used in thedescription on position such as top, bottom, side etc. refer to theFigure being described at the time, and where there is a change ofposition should be adjusted to the new position accordingly.Furthermore, individual features or combinations of features from theshown and described embodiments can in themselves represent independent,inventive solutions.

FIG. 1 shows an inkjet printing apparatus 1 with a printing head 2.

The inkjet printing apparatus 1 comprises three tanks 3 for holdingvarious inks and a tank 4 for holding a cleaning medium, whereby thetanks 3, 4 are connected by feed lines 5 to a stop element 6 and aconnection opening 7. The connection opening 7 of the stop element 6 isconnected with a feed opening 8 of the printing head 2. The stop element6 of the inkjet printing apparatus 1 is in the present embodiment in theform of a multiway valve. Of course, it is also possible for each feedline 5 to have a separate valve and for the outlet openings of saidvalves to open into a common connection opening 7.

Thus several tanks 3, 4 for inks and/or a cleaning medium are arrangedin front of the connection opening 7 for the printing head 2, wherebythe tanks 3, 4 are connected by feed lines 5 to the connection opening 7and a stop element 6 is arranged between each tank 3, 4 and theconnection opening 7.

There is a reservoir 9 between the ink tanks 3 and the stop element 6 inthe path of the feed line 5. Said reservoirs 9 are arranged togetherwith the stop element 6 close to the printing head 2, whereby thereservoirs 9 are designed as pressure compensating containers. Betweeneach reservoir 9 and tank 3 for the ink there is also a return line 10.This makes it possible to convey ink from the reservoir 9 back into thetank 3 and has the advantage that if an ink is not in use and the stopelement 6 for this ink is closed the ink can be conveyed between thereservoir 9 and the tank 3 in a circuit, and thus the deposit ofelements or ingredients of the ink in the lines (feed line 5, returnline 10) is avoided.

The printing head 2 is designed in a known manner and comprises adistribution chamber 11 which is fed with ink via the feed opening 8 ata first end and at a second end releases ink to, in this case eight,spray devices 12. By activating the spray devices 12 the ink is ejectedthrough nozzles 13 arranged in a lower end region of the printing head 2and thus applied onto the medium to be printed.

In order to convey the inks or a cleaning medium from the tanks 3 or 4to the printing head a pump 14 is arranged in each of the feed lines 5.In order to prevent the penetration of impurities into the printing head2 a filter 15 is also arranged in the feed lines 5. Analogously a pump16 is arranged in each of the return lines 10.

A stop element 17 is arranged in each of the feed lines 5 between eachof the tanks 3 and the connected reservoir 9. A stop element 18 isarranged correspondingly in the return lines 10 between each of thetanks 3 and the reservoir 9 connected thereto. By means of these stopelements 17, 18 the reservoirs 9 can be separated from the respectivetanks 3 with regard to the pressure, so that a stable flow of ink to theprinting head 2 can be achieved.

As in order to use inks from some ink systems it may be necessary toincrease their temperature above room temperature, the tanks 3 areequipped with heating elements 20 and thermometers 21 respectively. Forthe same reason the printing head 2 or the reservoirs 9 are alsoequipped with a heating element 22 and a thermometer 23. Of course it isalso possible for the tanks 3 or the reservoirs 9 to be provided with acommon heating element 20 or a common heating element 22. Accordingly itis sufficient in most cases if the tanks 3 or the reservoirs 9 only havea common thermometer 21 or a common thermometer 23.

For the automated control of the entire inkjet printing apparatus 1 thelatter is equipped with a control device 24. The stop element 6 in theform of a multiway valve is driven by the control device 24 in such away that only one of the feed lines 5 is ever connected continuouslywith the connection opening 7, and thus the feed opening 8 of theprinting head 2. From the tank 3 of which the feed line 5 is located inthe opened state relative to the connection opening 7, by means of thepump 14 ink is conveyed from the tank 3 via the corresponding reservoir9 into the distribution chamber 11 of the printing head 2. Thecorresponding pump 14 is also controlled by the control device 24. Theconveyance of the ink from the reservoir 9 to the distribution chamber11 can thus be performed by the effect of gravity on the ink as well asby a separate pump (not shown) arranged between the reservoir 9 and thestop element 6.

In order to measure the filling height of the ink in the correspondingcontainers the tanks 3, the reservoirs 9 and the distribution chambers11 of the printing head 2 are equipped in their inner chamber with afilling height sensor 25. By means of said filling height sensors 25 thefilling height can be measured continuously by the control device 24connected therewith. In a preferred embodiment said filling heightsensors 25 are arranged respectively at an upper end of the tanks 3, 4,the reservoirs 9 or the distribution chamber 11. In order to equalisethe pressure with environmental pressure the reservoirs 9 and thedistribution chamber 11 of the printing head 2 are provided respectivelywith a ventilation opening 26. The ventilation opening 26 in turn has anair filter which prevents particles of dust entering the nozzles 13 ofthe printing head 2 and blocking the latter.

Alternatively, it is also possible for the printing head 2 not to haveits own ventilation opening 26 or filling height sensor 25. In thisvariant of the invention the distribution chamber 11 of the printinghead 2 is filled completely with ink and the pressure equalisation withthe environmental air pressure can be achieved by means of theventilation opening 26 of the corresponding reservoir 9 or low pressurecan be applied in order to prevent the ink running out. A pressurecontrol circuit is preferably connected to the ventilation opening 26 bymeans of which the pressure in the distribution chamber 11 or thecorresponding reservoir 9 can be set so that ink is prevented fromrunning out of the nozzles 13 of the printing head 2.

The operation of the pump 14 and the stop element 6 by the controldevice 24 is always performed in such a way that the filling height ofthe distribution chamber 11 and the reservoir 9 with ink remains withina prespecified range.

The control device 24 is thus designed in such a way that thedistribution chamber 11 of the printing head 2 or the reservoir 9 can befilled with ink thereby, whereby the filling can be semiautomatic aswell as fully automatic. By means of the filling height sensors 25 inthe tanks 3, 4 the control device 24 can also be used to refill thetanks 3, 4 with the corresponding inks or a cleaning medium from refillcontainers connected thereto and set up separately from the inkjetprinting apparatus. In this manner the inkjet printing apparatus can beoperated without interruption.

The corresponding tank 3 and the reservoirs 9 and the printing head 2are held by heating element 20 or heating element 22 at the operatingtemperature required for the corresponding ink, whereby the actualtemperature is determined by the thermometer 21 or 23 in cooperationwith the control device 24 and thus the maintenance of the operatingtemperature can be monitored.

If the inkjet printing apparatus or the inkjet printer needs to be resetto print a different medium it is necessary in most cases for the inkjetprinting apparatus to be converted to work with ink from a different inksystem, i.e. inks of a different kind. By means of the inkjet printingapparatus 1 according to FIG. 1 this is made possible in an advantageousmanner in that the printing head 2, i.e. its distribution chamber 11 andits spray devices 12 with nozzles 13, are firstly cleaned with acleaning medium. For this the stop element 6 in the form of a multiwayvalve is adjusted by the control device 24 so that the feed line 5 ofthe tank 4 or the connection opening 7 is moved into the open position.By controlling the pump 14 of the tank 4 cleaning medium is then pumpedinto the printing head 2. By operating the spray devices 12simultaneously the residue of the remaining ink is removed from theprinting head 2 and the distribution chamber 11, the spray devices 12and the nozzles 13 are cleaned.

In addition to this cleaning process by feeding through the cleaningmedium it is also possible for compressed air to be blown into theprinting head 2 through a separate feed line (not shown), and thus anyresidue of cleaning medium residing in the printing head 2 is removedfrom the printing head 2. It is of course necessary for the ventilationopening 26 of the printing head 2 to be closed by a corresponding valve(not shown). It is particularly advantageous to design the ventilationopenings 26 of the printing head 2 and the reservoir 9 as a pressurecontrol valve or a servo valve.

In an alternative variant of the invention it is also possible insteadof using a cleaning medium to blow the “old” ink out by applying excesspressure to the ventilation openings 26.

For the process of ejecting remaining ink residue or cleaning medium theinkjet printer is designed to have a corresponding collecting device,such as e.g. an ink absorption pad or a suitable collection container.

After this cleaning process has been completed the stop element 6 is setby the control device 24 so that the feed line 5 of the respective tank3 with the ink of the new ink system is opened so that ink can flow outof the corresponding reservoir 9 into the distribution chamber 11 of theprinting head 2. By operating the corresponding pump 14 the ink issimultaneously conveyed out of the corresponding tank 3 into thecorresponding reservoir 9. As described above the filling height of thedistribution chamber 11 and the reservoir 9 is measured by means of thefilling height sensors 25 and the control device 24, and thus keptwithin a prespecified range.

It should be noted in particular that the individual parts of the inkjetprinting apparatus 1 and the printing head 2 in FIG. 1 are not true toscale and are simplified. In particular the volume of the tank 3 or 4 inthe actual and practical embodiment of a corresponding inkjet printingapparatus is a multiple of the volume of the distribution chamber 11 ofthe printing head 2 or the reservoir 9. In addition it should also benoted that the feed lines 5, the return lines 10 and the signal lines orthe supply lines between the control device 24 and the stop element 6 orthe filling height sensor 25, the heating elements 22 and thethermometers 23 are not rigid connections but are designed as flexiblelines or connections. During the printing process the printing head 2and the reservoirs 9 are moved at times at very high speeds andaccelerations over the medium to be printed, so that it is an advantageif the tanks 3 or 4 and the pumps 14 are attached to a part of theinkjet printer which is at rest compared to the printing head 2.

One colour of an ink system can be used by means of such a printing head2. If the same printing head 2 is a component of an inkjet printingapparatus 1, according to FIG. 1, it is possible to change between twodifferent ink systems, i.e. to the same colour of a different inksystem. For a complete inkjet printing apparatus it is of coursenecessary for each further colour to be used, to have the samearrangement of a printing head 2 and the additional components orelements, as shown in FIG. 1. The tanks 3, the feed lines 5, thereservoirs 9, the return lines 10, the stop elements 6 the pumps 14 andthe filters 15 are designed for holding inks from different ink systemsas well as different colours. Furthermore, the tank 4 and thecorresponding feed line 5, the corresponding pump 14 and thecorresponding filter 15 are designed for a cleaning medium in the formof a cleaning liquid, said parts can also be designed for holdingcompressed air as a cleaning medium.

FIG. 2 shows a printing head 2 with two reservoirs 9 and a feed opening27 for a cleaning medium. The printing head 2 is thus connected via thefeed lines 5 to two tanks 3 for inks or a tank 4 for a cleaning medium.

At a first end the two reservoirs 9 of the printing head 2 are connectedby a feed opening 8 with the connection opening 7 of a feed line 5. Atits second end the reservoirs 9 are connected by stop elements 6 to thedistribution chamber 11 or an upper end of the—in this embodimenteight—spray devices 12. The feed opening 27 for the cleaning medium isalso connected by a stop element 6 to the upper end of the spray devices12. At their first ends the reservoirs 9 also have a ventilation opening26 equipped with an air filter. The air filter prevents dust particlesentering the printing head 2 and causing a blockage in the nozzles 13.

As already described in the description of the FIG. 1, preferably apressure control circuit is preferably connected to the ventilationopening 3, by means of which the pressure can be adjusted on the insideof the printing head 2 so that ink cannot be escape by mistake throughthe nozzles 13, i.e. without operating the spray device 12.

A pump 14 and a filter 15 are arranged respectively in the feed lines 5of the tank 3 for the inks or the tank 4 for the cleaning medium. Theinks or the cleaning medium can be conveyed by the pumps 14 into theprinting head 2. The filters 15 can prevent impurities coming out of thetanks 3 or 4 into the printing head 2. In order to control the inkjetprinting apparatus 1 the latter is equipped with the control device 24.The control of the various operating states of the inkjet printingapparatus 1 can thus be automated or program controlled as well as semiautomated, i.e. by the manual input of parameters into a control panel(not shown) of the control device 24 or by the manual adjustment of thevarious operating states.

In order to control the supply of ink or cleaning medium the controldevice 24 is connected to the pumps 14, the stop elements 6 and also thefilling height sensors 25. In order to keep the inks during their use atthe required operating temperature the tanks 3 or the printing head 2are equipped with the heating elements 20 or 22 and thermometers 21 or23. In order to regulate the operating temperature of the inks saidheating elements 20 or 22 and the thermometer 21 or 23 are alsoconnected to the control device 24.

By opening one of the stop elements 6 of one of the two reservoirs 9 inkcan flow out of the reservoir 9 into the spray devices 12, so that inthis way the supply of spray devices 12 with a corresponding ink fromthe corresponding ink system is ensured. The flow of ink from thereservoir 9 into the region of the spray devices 12 is thus ensured inthat there can be equalisation of pressure through the ventilationopenings 26. If by the filling height sensors 25 in cooperation with thecontrol device 24 the filling height in the reservoir 9 is seen to fall,the control device 24 drives the corresponding pump 14 so that asufficient amount of ink is put into the reservoir 9 from thecorresponding tank 3.

In a further embodiment of the printing head according to FIG. 2 it isalso possible in an advantageous manner for the stop elements 6 to be inthe form of a common multiway valve.

The ejection of ink through the nozzles 13 in the lower end region ofthe spray devices 12 is performed in a known way by operating the spraydevices via corresponding data lines (not shown) or a correspondingcontrol device (not shown) of the inkjet printer.

The spray devices 12 are also equipped with an actuator 28 and a liquiddiode 29. The actuator 28 can be in the form of an electro restrictiveelement which is arranged on an outer wall of an elastically deformablehousing wall of the nozzle head 2 in the region of the spray device 12.If on the actuator 28 designed as an electro restrictive element thereis electric current a pressure impulse is exerted on the ink located inthe region of the spray device, so that the ink is moved on the one handin the direction of the nozzle 13 and on the other hand in the directionof the liquid diode 29. By means of the liquid diode 29 the movement ofink from the actuator 28 in the direction of the liquid diode 29 ismainly suppressed so that as a result a drop of ink is ejected from thenozzle 13 onto the medium to be printed. Alternatively, it is alsopossible to design the actuator 28 in the form of a correspondingheating element so that ink is heated so high in the region of the spraydevice 12 that it forms a bubble of steaming ink, which finally leads tothe ejection of a drop of ink from the nozzle 13. The actuator 28 can ofcourse also cause the ejection of ink by a different physical effect,e.g. electrostatically.

If the inkjet printing apparatus needs to be adjusted for working inksof a different ink system firstly the stop elements 6 of the inkreservoir 9 are closed and the locking elements 6 allocated to the feedopening 27 is opened for feeding a cleaning medium. The pump 14allocated to the tank 4 is then driven by the control device 24 so thatthe cleaning medium is conveyed into the nozzle 2 and through the spraydevices 12 and the nozzles 13. In this way the ink residue from thenozzle 2 remaining in the region of the spray devices 12 and the nozzles13 is removed and these areas are cleaned. In addition to cleaning witha cleaning medium in the form of a cleaning liquid it is also possiblefor compressed air to be blown by the pump 14 into the printing head 2and the spray devices 12 and the nozzles can be cleaned of the remainingresidue of cleaning liquid.

As already explained in the description of FIG. 1 the inkjet printer isprovided with a collecting device for the described procedure ofejecting remaining ink residue or the cleaning medium, such as e.g. anink absorption pad or a suitable collecting container.

After the described cleaning process the corresponding stop element forthe ink of the new ink system is opened by the control device 24 so thatthe ink can flow into the spray devices 12 and the nozzles 13. Thus theinkjet printing apparatus is adjusted for working with inks from the newink system. For inkjet printing apparatus which are to be used with inksystems of more than one colour, it is of course necessary that for eachof the colours there is an apparatus with the elements, as shown in FIG.2. It is of course also possible to have only one common control device24.

As explained in the description of FIG. 1 it should be stressed that theindividual parts are not true to scale and are simplified. Thus thevolumes of the tanks 3 or 4 in the actual and practical embodiment of acorresponding inkjet printing apparatus are a multiple of the volume ofthe reservoir 9 of the printing head 2. Likewise the feed lines 5 andthe various connections between the control device 24 and the stopelement 6, the pumps 14 and the heating elements 20 or 22 and thethermometers 21 or 23 and the filling height sensors 25 are designed tobe flexible.

FIG. 3 shows a detail of an inkjet printer with three inkjet printingapparatus 1 according to FIG. 2, in a perspective and much simplifiedview.

A printing medium 36 is moved in one direction 38 by a transport device37 comprising rollers. Three printing heads 2 are secured in a slide 39so that the latter can be moved at a small distance over the printingmedium 36 in lateral direction i.e. in a direction 40 perpendicular tothe direction 38 of the movement of the printing medium 36. In order tomove the slide 39 in transverse direction (direction 40) the latter isguided along two transverse guide tracks 41. During this movement of theprinting heads 2 over the printing medium 36 the printing medium 36 isprinted with the ink ejected from the printing heads 2. The ink is thusconveyed from the corresponding tanks 3 through the pumps 14 and thefeed lines 5 into the printing heads 2. The feed lines 5 and the dataand control lines (not shown) are in addition, in a known manner guidedthrough a flexible guide channel 42. In this way one end of the guidechannel 42 is secured to a fixed part of the frame (not shown) of theinkjet printer, whilst the second end region of the guide channel 42 issecured to the slide 39.

In order to keep the inks in the feed lines 5 at the required operatingtemperature the latter are connected with a heating element (not shown)and a thermometer (not shown). Of course it is also possible—inparticular over the course of the guide channel 42—for the supply lines5 to be connected to a common heating element and/or a commonthermometer.

In the case of high performance modern inkjet printers the movement ofthe slide 39 with the printing heads 2 is performed partly at highaccelerations. The acceleration forces acting on the ink in the printingheads 2 can lead to undesirable pressure fluctuations of the ink in thespray devices 12 or in the nozzles 13 (FIG. 1, FIG. 2). As a result thiscan cause fluctuations in the volume of the drops of ink ejected throughthe nozzles 13 or the suction of air or the deposit of ink and thusworsen picture quality. In order to avoid the corresponding pressurefluctuations, as already described in FIGS. 1 and 2, the distributionchamber 11 or the reservoirs 9 are designed to have ventilation openings26 or pressure control circuits are connected to ventilation openings26. By means of these ventilation openings 26 it is possible to equalisethe pressure with the environmental pressure. In order to avoiddifferences in pressure between different spray devices 12 of a printinghead 2 (a system of communicating vessels) the spray devices 12 or thenozzles 13 are aligned perpendicular to direction 40, i.e. perpendicularto the transverse direction of the slide 39. A third measure foravoiding variations in pressure is finally that the feed lines 5 or thereturn lines 10 as well as the lines between the stop element 6 and theprinting head 2 are made of an elastically restorable deformablematerial. In particular the said lines are designed to be elasticallyrestorable with a predeterminable force in radial direction.

With the inkjet printing apparatus 1 according to FIG. 1 or FIG. 2 it ispossible to manufacture inkjet printers which permit simple conversionfor processing inks from different ink systems. By designing inkjetprinters with inkjet printing apparatus 1 according to the invention thecorresponding inkjet printers can be used universally with very shortconversion times. The further elements of such an inkjet printer are onthe one hand a transport device for a medium 36 to be printed and on theother hand a transport device or a drive for moving the printing heads 2over the printing medium 36. A corresponding inkjet printer also has acontrol device which is connected with the drives for the transportdevice for the printing medium 36 and the transport device for nozzleheads 2 or the slide 39, and a system of data lines or a data networkwhich can be controlled by the control device of the printing heads 2 insuch a way that from the image information data the corresponding imagecan be applied to the medium 36 to be printed. In the case of inkjetprinters with a plurality of printing heads 2 it is of course alsopossible that several printing heads 2 use the same colour. It is alsopossible that tanks 3 with several inkjet printing devices 1 for inks ofthe same ink system and the same colour are formed respectively bycommon tanks 3.

For form's same it should be pointed out that for a better understandingof the structure of the inkjet printing apparatus or the printing headthe latter or their components are not always drawn to scale and/or havebeen enlarged and/or reduced in size.

The objective forming the basis of the independent solutions of theinvention can be taken from the description.

Mainly the individual designs shown in FIGS. 1; 2; 3 can form thesubject of independent solutions according to the invention. Theobjectives and solutions of the invention can be taken from the detaileddescriptions of said figures. List of Reference Numbers 1. Inkjetprinting apparatus 2. Printing head 3. Tank 4. Tank 5. Feed line 6. Stopelement 7. Connection opening 8. Feed opening 9. Reservoir 10. Returnline 11. Distribution chamber 12. Spray device 13. Nozzle 14. Pump 15.Filter 16. Pump 17. Stop element 18. Stop element 19. 20. Heatingelement 21. Thermometer 22. Heating element 23. Thermometer 24. Controldevice 25. Filling height sensor 26. Ventilation opening 27. Feedopening 28. Actuator 29. Liquid diode 36. Printing medium 37. Transportdevice 38. Direction 39. Slide 40. Direction 41. Transverse guide track42. Guide channel

1-38. (canceled)
 39. Inkjet printing apparatus with at least oneprinting head, whereby several tanks (3, 4) for inks and/or a cleaningmedium are arranged in front of a connection opening (7) for theprinting head (2), and the tanks (3, 4) are connected by feed lines (5)with the connection opening (7) for the printing head (2), and whereby astop element (6) is arranged between each tank (3, 4) and a distributionchamber (11) of the printing head (2), wherein the tanks (3, 4) for theinks and/or the printing head (2) are designed to have a heating element(20, 22) and/or a thermometer (21, 23).
 40. Inkjet printing apparatusaccording to claim 39, wherein a reservoir (9) is arranged in the feedline (5) between the stop element (6) and the tank (3, 4).
 41. Inkjetprinting apparatus according to claim 39, wherein the reservoir (9) isdesigned as a pressure compensating container, and/or for applying lowpressure.
 42. Inkjet printing apparatus according to claim 39, whereinat least one reservoir (9) is arranged in the printing head (2). 43.Inkjet printing apparatus according to claim 39, wherein the stopelement (6) is designed as a multiway valve.
 44. Inkjet printingapparatus according to claim 39, wherein a pump (14) is arranged betweeneach tank (3, 4) and the connection opening (7).
 45. Inkjet printingapparatus according to claim 39, wherein a filter (15) is arrangedbetween each tank (3, 4) and the connection opening (7).
 46. Inkjetprinting apparatus according to claim 39, wherein a stop element (17) isarranged in the feed line (5) between each tank (3) and the reservoir(9) connected therewith.
 47. Inkjet printing apparatus according toclaim 39, wherein a stop element (18) is arranged in the return line(10) between each tank (3) and the reservoir (9) connected therewith.48. Inkjet printing apparatus according to claim 39, wherein thereservoirs (9) are designed to have a heating element (20, 22) and/or athermometer (21, 23).
 49. Inkjet printing apparatus according to claim39, wherein the tanks (3, 4) are designed to have a common heatingelement (20) and/or a common thermometer (21).
 50. Inkjet printingapparatus according to claim 39, wherein the feed lines (5) areconnected with a heating element and/or a thermometer.
 51. Inkjetprinting apparatus according to claim 39, wherein a common heatingelement and/or a common thermometer is allocated to several feed lines(5).
 52. Inkjet printing apparatus according to claim 39, wherein theprinting head (2) is designed to have a heating element (22) and/or athermometer (23).
 53. Inkjet printing apparatus according to claim 39,wherein the tanks (3, 4), the feed lines (5), the reservoirs (9), thestop elements (6), the pumps (14, 16) and the filters (15) are designedfor holding inks of different ink systems and/or different colours. 54.Inkjet printing apparatus according to claim 39, wherein the tanks (3,4), the feed lines (5), the reservoirs (9), the stop elements (6), thepumps (14, 16) and the filters (15) are designed for holding a cleaningfluid and/or compressed air as a cleaning medium.
 55. Inkjet printingapparatus according to claim
 39. wherein a tilling height sensor (25) isarranged in an inner chamber of the reservoir (9) and/or the tank (3, 4)and/or a distribution chamber (11) for the inks.
 56. Ink jet printingapparatus according to claim 39, wherein the filling height sensor (25)is arranged in an upper end region of the reservoir (9) and/or the tanks(3, 4) and/or the distribution chamber (11).
 57. Inkjet printingapparatus according to claim 39, wherein the reservoir (9) for the inksis designed to have at least one ventilation opening (26).
 58. Inkjetprinting apparatus according to claim 39, wherein the distributionchamber (11) of the printing head (2) is designed to have at least oneventilation opening (26)
 59. Inkjet printing apparatus according toclaim 39, wherein a pressure control valve, in particular a servo valve,is arranged in the ventilation opening (26).
 60. Inkjet printingapparatus according to claim 39, wherein a pressure control circuit isconnected to the ventilation opening (26).
 61. Inkjet printing apparatusaccording to claim 39, wherein an air filter is arranged in theventilation opening (26).
 62. Inkjet printing apparatus according toclaim 39, wherein the feed line (5) is designed to be elasticallyrestorable.
 63. Inkjet printing apparatus according to claim 39, whereinthe feed line (5) is designed to be elastically restorable with aprespecifiable force in radial direction.
 64. Inkjet printing apparatusaccording to claim 39, wherein the reservoir (9) is connected by areturn line (10) and a pump (16) to the tank (3, 4).
 65. Inkjet printingapparatus according to claim 39, wherein tanks (3, 4) are connected viaindependent stop elements (6) to several printing heads.
 66. Inkjetprinting apparatus according to claim 39, wherein the stop elements (6,17, 18) and/or the pumps (14, 16) and/or the filling height sensors (25)and/or the heating elements (20, 22) and/or the thermometers (21, 23)are connected to a control device (24).
 67. Inkjet printing apparatusaccording to claim 39, wherein the control device (24) is designed forcontrolling the filling of the distribution chamber (11) and/or thereservoir (9) with ink.
 68. Inkjet printing apparatus according to claim39, wherein the control device (24) is designed for filling tank (3)with ink and/or for filling tank (4) with cleaning medium.
 69. Printinghead for inkjet printing apparatus with a distribution chamber (11) forreleasing ink into one or more spray devices (12) and with a ventilationopening (26), wherein in the printing head (2) several reservoirs (9)for inks and/or a cleaning medium are formed each with a feed opening(8, 27) at a first end of the reservoir (9) and a stop element (6)between a second end of the reservoir (9) and the distribution chamber(11) of the spray device (12).
 70. Printing head according to claim 69,wherein the reservoir (9) for the inks is designed to have at least oneventilation opening (26).
 71. Printing head according to claim 69,wherein a pressure control valve, in particular a servo valve, isarranged in the ventilation opening (26).
 72. Printing head according toclaim 39, wherein a pressure control circuit is connected to theventilation opening (26).
 73. Printing head according to claim 39,wherein an air filter is arranged in the ventilation opening (26). 74.Printing head according to claim 39, wherein the printing head (2) isdesigned to have a heating element (22) and/or a thermometer (23). 75.Printing head according to claim 39, wherein the reservoirs (9), thedistribution chambers (11), the stop elements (6) and the spray device(12) are designed for holding inks of various ink systems and variouscolours.
 76. Printing head according to claim 39, wherein the reservoirs(9), the distribution chambers (11), the stop elements (6) and the spraydevice (12) are designed for holding a cleaning liquid and/or compressedair as a cleaning medium.